3rd century
After it
separated from Judaism, Christianity became an illegal religion in Roman
empire and was persecuted by emperors. The Churcheˇ¦s attitude towards the
Empire was outside of the state, but sometimes some bishops occasionally
appealed to imperial authority to enforce their decisions they had made, such
as removal of Bishop.

4th Century
Constantine changed the situation of Christianity from illegal to tolerate and
support. The State began to be involved in matters of the church. For example,
Emperors called the councils which tried to settle the doctrinal unity of the
church. In the new imperial city, Constantinople, only Christianity was
practiced; no other religionsˇ¦ traditional rites were allowed. Apparently,
Constantine and his sons intended to use the church as a means of unification
of the empire. Most Roman emperors after Constantineˇ¦s line were committed to
Christianity, but primarily as a means of securing their control over the
empire.

5th Century
476, the Western empire falls. The popes turned to the
rising power of the new peoples in the west to secure their independence from
Constantinople. The church has an alliance with the Franks. The Eastern church
maintained the alliance with Eastern empire untill 1453.

6th Century
Many barbarian tribes established their own states in
the west. The mission work of the church made many states convert to
Christianity, such as Kent of Britain.

7th-9th Century
The church needs financial support and military
protection from the king. The king needs the alliance with Pope and needs Pope
to declare the king a legal emperor or authority. For instance, Pippin gave
the land to the Pope as a gift for the alliance with the Pope. Another
example, the Pope, Leo III placed a crown on Charlemagne and declared him to
be the Holy Roman emperor because he conquered over Saxon tribes that were the
threat of the church and forced them to convert to Christianity.

10th-14th Century
The church had its own army. The Crusades was called by
the Pope for a holy war. At this time, the military power of the church was
stronger than the state so that it can protect not only the church, but also
the state. The Pope became the highest leaders of Europe. On the other hand, a
series of councils were called by popes. Before this time, all the prior
councils had been called and controlled by emperors.

Three
theories of the relationship between the church and the state

After the
promotion of Christianity in the 4th C.E., Roman Empire gradually became a
Christian empire and began to be involved in the affairs of the church. The
church had to develop political theologies to understand and regulate its
relationship with the empire (state).

Eusebiusˇ¦s theory: The church
cooperate with the state
He looked
positively on the Christian empire, and adopted the notion of a single
society, which is under the guidance of the emperor, once the emperor had
become Christian. Empire was regarded as an instrument of Christˇ¦s victory.
Empire promoted true religion and suppresses idolatry, and has responsibility
for the Church. The Church has a limited degree of independence. The Eastern
churches tended to accept this theory.

Ambroseˇ¦s theory: The church must
be independent from the state
He used
Old Testament model of high priest and king to interpret the relation between
bishop and emperor. The church must be completely independent from the empire
and cannot be controlled by the king, especially on doctrinal issues.
Moreover, the bishop could call the king to repent and follow Godˇ¦s law. For
example, Ambrose called the king to repent for having ordered of a massacre.

Augustineˇ¦s theory: Two kinds of
invisible forms of human association
There are
two kinds of cities or forms of human association: City of God and the earthly
city. The citizens of the City of God love God while those in the earthly city
love self. Cities are defined by intention, are not visible social
institutions. The Christian church cannot be identified with the City of God
on earth because it contains persons who are evil. The state need not be evil.
The state has its own role within earthly temporal realm. Its goals are to
secure the good, people life, and the church. Christians can and even should
work in the state to help the state achieve its goals.